HTLV III or Human T-cell Leukemia Virus Type III, now commonly referred to as Human Immunodeficiency Virus ("HIV") is recognized to be the causative agent for human immunodeficiency syndrome or AIDS. The chronic nature of AIDS considered as approaching epidemic proportions in the United States and other countries is reflected by perfusion of studies and efforts to develop diagnostic immunoassays for reliably and consistently detecting viral antigens and antibodies to such antigens in human peripheral blood. In substantial measure, monoclonal antibody technology has been recorded to for developing such immunoassays.
HIV belongs to the retrovirus group of viruses. Retroviruses carry a positive-stranded RNA and a special enzyme called reverse transcriptase in its core which is used to convert viral RNA into DNA. This reverses the classical process of cellular transcription in which DNA is converted to RNA.
It is known that the HIV binds to T4 lymphocytes because the T4 protein on the surface of T4 lymphocytes serves as a receptor or binding site for HIV [Dalgleish AG et al., Nature 312:763-767 (1985)]. HIV also can bind to and attack other cells, such as, monocytes, tissue macrophages, and cells in the brain, spinal cord and peripheral nerves. The life cycle of HIV calls for the virus entering the host patient through sexual activity or blood transfusion, for instance, and then binding to receptors on monocytes and lymphocytes. The virus penetrates the cell and sheds its envelope or protein coat so as to expose its viral RNA core. The reverse transcriptase converts the viral RNA core to DNA which is integrated into the host cell genome. New viral particles are produced in quantity until the membrane of the host cell is ruptured to release the new viral particles in the human blood system.
HIV is comprised of protein molecules which form an enclosure membrane or envelope and a core which covers the viral RNA antigens. There are antigens expressed on the membrane and in the core materials; the core has the major portion of the proteins comprising the virus. While the general technology for producing monoclonal antibodies from cell lines is widely used and understood theoretically, the complications and variations encountered in attempting to produce specific antibodies is well recognized. Each investigation into specific monoclonal antibody development and production raises its own obstacles to successful implementation. Success or lack of success in any particular project is related in great measure to the nature of the antigen involved and techniques used to effect cell fusion and isolation of the appropriate hybridoma. These obstacles are particularly evident where production of a cell line which will produce monoclonal antibodies specific to the HIV virus is concerned. The HIV being comprised of an envelope membrane with a myriad of antigenic determinants and a core protein expressing a myriad of antigenic sites, it will be readily understood that ordinary fusion of myeloma cells and spleen cells of immunized mice will evolve an astronomical number of hybridomas and screening thereafter for specific antibodies will be a monumentally complicated exercise.
Monoclonal antibodies which recognize viral proteins of HIV isolates were studied in Ferns et al., J. Gen. Virol., 68:1543-1551 (1987-Great Britain). The monoclonal antibodies were raised against the gag proteins of the HIV. A panel of monoclonal antibodies were characterized by Western blot to establish the HIV gag proteins recognized by the monoclonal antibodies as proteins of 55,000 dalton molecular weight (p55), 24000 dalton molecular weight (p24), 18000 dalton molecular weight (P18), all core antigens.
The entire genome of the HIV has been sequenced in the study of Serki et al., Proc. Natl. Acad. Sci., 80:3618-3622 (1983). This study showed the various glycosylated proteins of the HIV envelope genes and that the core proteins are not glycosylated proteins. The study of Ferns et al., supra, shows that the glycosylated proteins of the HIV envelope gene are identified as gp 160, indicating a molecular weight of 160,000 daltons, gp 120, indicating a molecular weight of 120,000 daltons and gp 41, indicating a molecular weight of 41,000 daltons.
Diagnostic tests commercially available at this time utilizing monoclonal antibodies to determine whether a person having the AIDS disease or has been immunologically exposed to the virus can be identified have been less than successful. Diagnosis of the disease is complicated by the fact that extended periods of incubation are required before symptoms of the disease are expressed. The highly infectious nature of the disease and the fact that its cure presently is not within scientific capability also increases the difficulty of investigating live virus and its adverse affect on the human immune system so that successful diagnostic tests can be developed.
An object of this invention is to provide a hybridoma or hybrid cell line which produces a novel monoclonal antibody which binds to selective major proteins in the core. This monoclonal antibody recognizes a common epitope of certain HIV core antigens consistently and reliably so that said antibody can be employed in immunoassays to track HIV viral antigens in a human physiological serum sample with great accuracy. This monoclonal antibody does not bind HIV envelope antigens.